clarify namespace in double_contraction of SymmetricTensor
clarify namespace in double_contraction of SymmetricTensor

MSVC stumbled over this.

shakirbsm/dealii,kalj/dealii,kalj/dealii,JaeryunYim/dealii,ESeNonFossiIo/dealii,kalj/dealii,maieneuro/dealii,nicolacavallini/dealii,angelrca/dealii,angelrca/dealii,sairajat/dealii,gpitton/dealii,naliboff/dealii,shakirbsm/dealii,maieneuro/dealii,gpitton/dealii,danshapero/dealii,JaeryunYim/dealii,ESeNonFossiIo/dealii,spco/dealii,angelrca/dealii,maieneuro/dealii,gpitton/dealii,sairajat/dealii,jperryhouts/dealii,shakirbsm/dealii,Arezou-gh/dealii,nicolacavallini/dealii,spco/dealii,jperryhouts/dealii,EGP-CIG-REU/dealii,JaeryunYim/dealii,EGP-CIG-REU/dealii,naliboff/dealii,shakirbsm/dealii,danshapero/dealii,andreamola/dealii,sairajat/dealii,danshapero/dealii,ESeNonFossiIo/dealii,pesser/dealii,naliboff/dealii,spco/dealii,jperryhouts/dealii,gpitton/dealii,ESeNonFossiIo/dealii,EGP-CIG-REU/dealii,gpitton/dealii,spco/dealii,kalj/dealii,nicolacavallini/dealii,angelrca/dealii,andreamola/dealii,Arezou-gh/dealii,andreamola/dealii,danshapero/dealii,spco/dealii,pesser/dealii,pesser/dealii,nicolacavallini/dealii,angelrca/dealii,ESeNonFossiIo/dealii,gpitton/dealii,spco/dealii,shakirbsm/dealii,EGP-CIG-REU/dealii,kalj/dealii,ESeNonFossiIo/dealii,gpitton/dealii,sairajat/dealii,jperryhouts/dealii,maieneuro/dealii,sairajat/dealii,Arezou-gh/dealii,nicolacavallini/dealii,Arezou-gh/dealii,ESeNonFossiIo/dealii,naliboff/dealii,EGP-CIG-REU/dealii,EGP-CIG-REU/dealii,sairajat/dealii,danshapero/dealii,andreamola/dealii,andreamola/dealii,shakirbsm/dealii,JaeryunYim/dealii,pesser/dealii,nicolacavallini/dealii,kalj/dealii,pesser/dealii,nicolacavallini/dealii,angelrca/dealii,pesser/dealii,sairajat/dealii,naliboff/dealii,JaeryunYim/dealii,shakirbsm/dealii,danshapero/dealii,Arezou-gh/dealii,jperryhouts/dealii,danshapero/dealii,andreamola/dealii,angelrca/dealii,maieneuro/dealii,jperryhouts/dealii,Arezou-gh/dealii,Arezou-gh/dealii,naliboff/dealii,JaeryunYim/dealii,andreamola/dealii,pesser/dealii,maieneuro/dealii,maieneuro/dealii,spco/dealii,naliboff/dealii,jperryhouts/dealii,kalj/dealii,JaeryunYim/dealii,EGP-CIG-REU/dealii